Here we discuss skill points, you recieve a skill point at the beginning of the game and one every 10 turns, while not as valuable asa location, a skill point is more numerous, please note that skill points cannot be stacked, but can work with other things like locations or an ability.
Here is a list of things you can spend a skill point into, some are basic like any armor or weapon upgrade can do, so may not be as valued as others, but it all depends on your strategy, in some cases it might be more valuable.
increase attack 50
increase health 50
increase defense 25
increase accuracy 10%
increase gold from mines by 100
(more to come)